Family and twin studies in inflammatory bowel disease

Table 1 Concordance rates for CD and UC according to three large twin studies

	Monozygotic twins		Dizygotic twins
	CD	UC	CD	UC
Halfvarsson[7]	50% (n = 18)	19% (n = 16)	4% (n = 26)	0% (n = 20)
Orholm[8]	50% (n = 10)	14% (n = 21)	0% (n = 27)	7% (n = 44)
Thompson[9]	20% (n = 25)	16% (n = 38)	7% (n = 46)	3% (n = 34)

Table 2 Recent studies on the occurrence (in percent) of affected first-degree relatives in a proband with CD and UC

	Proband with CD		Proband with UC
	First-degree relatives with CD	First-degree relatives withany form of IBD	First-degree relatives with UC	First-degree relatives with any form of IBD
Freeman (2002)[10]	8.7% (n = 1000)	-	-	-
Halme (2002)[11]	10.9% (n = 257)	15.6% (n = 257)	11.3% (n = 436)	13.8% (n = 436)
Carbonnel (1999)[12]	7.5% (n = 1316)	8.4% (n = 1316)	-	-
Peeters (1996)[13]	13.6% (n = 640)	14.5% (n = 640)	-	-
Bayless (1996)[14]	12.2 % (n = 554)	-	-	-
Satsangi (1994)[1]	-	11.5% (n = 433)	-	-
Probert (1993)[2]	9.4% (n = 424)	10.4% (n = 424)	7.1% (n = 469)	8.6% (n = 469)
Yang (1993)[15]	7.4% (n = 258)	14.0% (n = 258)	7.1% (n = 269)	8.6% (n = 269)
Orholm (1991)[5]	2.2% (n = 133)	5.2% (n = 133)	7.5% (n = 504)	8.1% (n = 504)